Do you have any plugins other than BuddyPress installed and activated? 3 plugin widgets of my own that display posts from the database

…AND…

Are you using the standard BuddyPress themes or customized themes? customised themes

To help you figure out what is going on, you need to distill your install down to the lowest common denominator. This means stripping out all extra stuff and focusing on the barebones environment.

So, you need to deactivate ALL plugins except BuddyPress. You need to use the default themes that come with BuddyPress. If the problems go away, then it is related to your custom theme and/or one of more of your plugins.

Here are a few more questions:

Which hosting firm are you using?

Did you manually install WPMU + BuddyPress or use a one-button installer?

There have been a few changes over time to WPMU’s wp-config.php file. If you simply used an older file this could also cause problems. Always verify that the config file you are using is up to date by comapring it to the config file that comes with each, newly downloaded WPMU install package. Did you use the wp-config.php file that came with WPMU 2.7.1?

I switched to the BuddyPress default themes… still failed with the media library duplicate, but I can add friends

Well, one problem isolated. So, this particular issue appears to be caused by your custom theme. Make sure that you compare the header file in the bpmember theme, or even the bpskeltonmember theme, with your custom header file. You could be missing a key line or two.

Concerning the duplicate declaration error: were you running an older version of BP before–like RC1? If so, did you delete all your old BuddyPress files from /mu-plugins/, this includes theme files.